The ventilation systems are becoming more compact so as to save buildings space. In return, the velocity, in ventilation units, is increased and the air flows are also more turbulent. The hotwire investigation aims to correlate this increase of turbulence with the increase of the noise level. The investigation was done for industrials purposes and is based on empirical researches completed with theoretical knowledge. For the investigation, the hotwire sensor is chosen for its ability to detect small velocity fluctuations at high frequency. Two different prototypes are designed in order to highlight the influence of the turbulence level in the sound generation, especially at ventilation outlets. A procedure is also introduced, in which the hotwire is used for the turbulence measures and a reverberation room for the sound measurement. General conclusions are finally identified and explain the influence of the turbulence in the sound generation mechanisms. The influence of the prototypes geometries, on both the sound and the turbulence, is analyzed and the master thesis describes how the air flow velocity in ducts and the static pressure could modify both the turbulence and the sound levels. The stated conclusions imply that the designers of new ventilation systems should take into account the turbulence generated by their experimental product if they want to conserve good sound properties.

Rotary machinery systems are widely used in different industries. As they have rotational movements, the resonances will be the function of rotational speed. Nowadays, there are different CAE (Computer Aided Engineering ) softwares that use finite element method to solve complex problems by simplifying the model to a limited DOF (Degree Of Freedom) system. Some of the CAE software have built-in module for rotary machinery to solve eigenvalue problems, unbalance response, stability, etc. COMSOL multiphysics 1 is a CAE software that can deal with structural mechanics. There is not any specific module for the rotor dynamics analysis in COMSOL multiphysics version 4.2a; however, It is possible to make a model based on 1D beam elements or even structural mechanics elements and solve the problem by using equivalent gyroscopic moment and unbalance force terms. The scope of this thesis is based on 1D beam element solution. Moreover, the result of the COMSOL solution has been compared with ANSYS based on 3D element 2. In this thesis, the main purpose is implementing rotor dynamics concepts in COMSOL multiphysics based on beam element 3 . Second chapter is focused on the theory part of the rotordynamics where the equations in the stationary cases are derived which measn the rotational speed of the rotor does not change by time; moreover, a brief overview of finite element method has been mentioned. The third chapter covers the implementation of the rotor dynamics in COMSOL where a very brief overview of different COMSOL’s sections that are used in this thesis are described; Moreover, load implementation , 3D mapping based on extrusion integration and comparison a result data with ANSYS are mentioned. In the fourth chapter rotordynamics analysis is described based on Campbell plot 4, stability analysis and harmonic response from a model that is made in COMSOL. Final chapter is the conclusion part about this thesis based on the results that have been shown.

In ABB, Soundplan is the usually used software to predict the industrial noise for power transmission plants. However, the sound sources in Soundplan are modeled as point sources between which there are no sound reflections. For the real situation, the sound sources are very big and can be regarded as noise barriers. So it is important to take the reflections between sound sources into consideration.COMSOL Multiphysics is Finite Element Method (FEM) software which can model acoustic object with sound-reflective boundaries. First, the COMSOL model for single component inside the power transmission plant will be discussed. Then the COMSOL model for the whole plant will be calculated at different frequencies. The total sound pressure level at different receivers will be compared between COMSOL and Soundplan results. COMSOL can be used to predict the sound propagation of the power transmission plant and it can give different results when the outline of the plant is changed.

Direct numerical simulation (DNS) of steady flow, with Re = 750 at inlet, through stenosed pipe has been done to study transition and turbulence of the flow in the post-stenosis area. The pipe has 75% constriction by area reduction and 5% eccentricity of the main pipe diameter at the throat. A sinusoidal Gaussian force is implemented to keep turbulent in the domain. The result shows acceptable agreement with previous study has  been done by Fischer et al. [4]. We simulated the case by NEK5000 which benefits from the spectral element method (SEM) as a higher order accurate method. To have a better understanding of the turbulent flow, we have done the modal decomposition to obtain coherent structures. Among several methods for modal decomposition, we considered Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) for current study. The methods have been implemented in Fortran, accelerated using OpenMP and is potentially settled for computation of large data sets. DMD implementation shows 2.5 speed up. The stuctures correspond to the implementation force are extracted by POD however they have not been recognised by dynamic decomposition.

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This thesis focuses on FEM analysis of paperboard global stiffness. Simulations in Abaqus and experiments were carried out where the deformation was measured. The experimental results were compared with simulation results in order to verify the FEM simulations. Different types of boxes were used to carry out the empirical experiments. The analyses are based on one model that simulates the mechanic behavior of the used boxes. The influence of the creasing stiffness in the global stiffness is specially analyzed. Different gluing zones, materials and structural geometries were used in boxes. The model predicted the experimental results well except from the gluing zones that in some experiments had a higher impact concluding in worse results. Moreover, the results of the work indicate that the deformation of the boxes mostly depend on the bending stiffness of the paperboard while the influence of the creasing stiffness is low.

I det här arbetet undersöks hur väl Effective notch-metoden, postprocessorn FEMFAT samt en metod som utnyttjar en ekvivalent spänning i svetsens närområde predikterar svetsförbands livslängder. För att få en uppfattning om metodernas förmåga att prediktera livslängd jämförs beräknade livslängder med livslängder erhållna vid Wöhlerprovning av fyra olika geometrier av pluggsvetsförband samt ett svetsat växlingslänkage. Målet är att finna en tidseffektiv och noggrann metod för modellering av de studerade förbandstyperna, en metod som på sikt kan användas för livslängdsprediktion oberoende av svetsförbandstyp och lastfall. Resultat visar att Effective notch-metoden är en konservativ metod som inte överskattar svetsförbandens livslängder. Då Effective notch-metoden minimerar risken att man råkar ut för oväntat haveri bör den användas vid svetsförbandsutvärdering trots att det inte är den tidseffektivaste metoden. FEMFAT visar stor variation och opålitlighet i resultaten och bör inte användas för svetsförband som inte finns fördefinierade i deras modelleringsguide. Metoden med ekvivalent spänning i svetsens närområde tenderar att överskatta livslängder om komponenten utsätts för en pulserande last medan goda resultat erhålls då lasten är växlande. Då metoden är väldigt enkel att använda kan den vara ett bra verktyg för att lokalisera kritiska svetsar i stora strukturer, men anses inte lämplig för noggrannare utvärdering av svetsförband.

The oil- and gas industry has increasingly begun to switch from oil platforms and instead started to install the modules, process stations, etc. directly on the seabed. Some parts are more sensitive to external loads than others, and it is crucial to protect them to avoid damage on the structures and even gas/oil leakage. Protection covers made of glass fiber reinforced plastic (GRP) is becoming more frequently used in the offshore industry due to its low cost and good mechanical properties. Common load cases that the GRP cover could be exposed to have been identified and an investigation has been carried out to see what influence different factors like lay-up sequence and the number of plies has on the GRP cover. A fast and effective working method for future projects regarding GRP covers has been developed with the usage of Ansys and Excel. Analysis showed that for the installation and trawl net friction load cases the number of failed layers are very much dependent on the lay-up sequence of the GRP cover. Installation should be done vertically in order to prevent ply failure. For the trawl impact and Trawl Over-Pull load cases the numbers of failed plies are almost independent of the lay-up sequence. The conclusion is that lay-up sequences of [0/90]s and [-45/45]s are the most appropriate ones for this type of GRP cover and for the considered load cases. A total of 48 plies were recommended to ensure a completely intact protection structure for installation and trawl net friction, and only get small local failure at the trawl impact and over-pull load cases.

Detta examensarbete undersöker armeringens inverkan på en förankringsskruvs utdrags-kapacitet. Simuleringar har genomförts i finita elementprogrammet Abaqus. Studien behandlar ett betongblock, 1.2x1.2x0.3 m, med en förankringsskruv i mitten av blocket. Skruven har en diameter på 30 mm och är 220 mm lång, varav de nedersta 20 mm omges av en mutter med diametern 45 mm. Undersökningar har gjorts för att se hur ytarmering påverkar konstruktionens kapacitet och hur, när och var det kommer spricka upp. Armeringen har lagts in som ett rutnät i både överkant och underkant av betongblocket och har varierats i täthet. För att skapa en bra modell har förberedande undersökningar gjorts på materialmodell, mesh, elementtyp, elementstorlek och om det går att förenkla modellen genom att ersätta skruven med randvillkor. Studien har sedan genomförts för sex olika fall av armeringstäthet. Resultatet visar att ju tätare armering desto mer utdragslast kan förankringsskruven ta upp. Avståndet mellan armeringen och förankringsfästet påverkar också. Ligger första armerings-stången nära förankringen klarar konstruktionen en större belastning än om armeringen är placerad längre ifrån. Plottar över största plastiska huvudtöjningen indikerar hur mikrosprickor kommer att ut-vecklas i betongen med start nära skruvskallen och med formen av en kon. Det finns också tendenser till att lutningen på konen blir brantare ju tätare armeringen är.

In this master thesis project the possibility to model the response of a wing when subjected to bird strike using finite elements is analyzed. Since this transient event lasts only a few milliseconds the used solution method is explicit time integration. The wing is manufactured using carbon fiber laminate. Carbon fiber laminates have orthotropic material properties with different stiffness in different directions. Accordingly, there are damage mechanisms not considered when using metal that have to be modeled when using composites. One of these damage mechanisms is delamination which occurs when cured layers inside a component become separated. To simulate this phenomenon, multiple layers of shell elements with contact in between are used as a representation of the interface where a component is likely to delaminate. By comparing experimental and simulated results the model of delamination is verified and the influence of different parameters on the results is investigated. Furthermore, studies show that modeling delamination layers in each possible layer of a composite stack is not optimal due to the fact that the global stiffness of the laminate is decreased as more layers are modeled. However, multiple layers are needed in order to mitigate the spreading of delamination and obtain realistic delaminated zones. As the laminates are comprised of carbon fiber and epoxy sheets it is of importance to include damage mechanisms inside each individual sheet. Accordingly, a composite material model built into the software is used which considers tensile and compressive stress in fiber and epoxy. The strength limits are then set according to experimental test data. The bird is modeled using a mesh free technique called Smooth Particle Hydrodynamics using a material model with properties similar to a fluid. The internal pressure of the bird model is linked to the change in volume with an Equation of State. By examining the bird models behavior compared to experimental results it is determined to have a realistic impact on structures. A model of the leading edge is then subjected to bird strike according to European standards. The wing skin is penetrated indicating that reinforcements might be needed in order to protect valuable components inside the wing structure such as the fuel tank. However, the results are not completely accurate due to the fact that there is little experimental data available regarding soft body penetration of composite laminates. As a consequence, the simulation cannot be confirmed against real experimental results and further investigations are required in order to have confidence in modeling such events. Furthermore, the delamination due to the bird strike essentially spreads across the whole model. Since only one layer of delamination is included the spread is most likely overestimated.